Please 1.) install the correct fonts from Microsoft or OS install CD and make sure that You have 2.) chosen the correct Encoding (View > Encoding).

p.s. 1.) If a font is not installed its letters/words are displayed as ?

2.) The browser engine tries to sniff the correct encoding.
Page and sever info overrules the findings of the engine.
(K-Meleon does not sniff if it is told by the page author, server.)
Your browser settings will overrule the page info.
So You may have to set the correct encoding by hand for Your Chinese words.

Else there can be errors in the page that are shown as ? or the author wanted ?

Example: This page has a German translation but gives me ? e.g. for umlauts ( umlaut = special German vowel ). I have to set the correct encoding (windows 1252) for K-Meleon by hand - if I want letters such as ä ö ü (umlauts corresponding with a o u) displayed properly. The reason for this behavior the page says:
<?xml version="1.0" encoding="UTF-8"?>

So if a web page tells the browser it is UTF8 & uses windows1252 instead the result is shown as ? if the bite code of the letter is not the same in both encodings.

I installed a fresh copy of K-Meleon 1.1.5, bone stock. My Windows XP Pro English has 'Language for non-Unicode programs' set to Chinese(Taiwan), which should map to Big5. East Asian language support is installed already. I use plenty of non-Unicode apps daily so I'm reasonably sure my OS is set up correctly at least for Big5. I then tried the two following webpages:

The same happens to German in this Forum.
The solution for German is to set the used/correct encoding by hand.
The 2 .cn respectively .jp pages show no ? if encoding utf16 is set via
View > Encoding (that is below Zoom) > UTF16 (bottom item).